How Optical Devices Enhance Learning and Daily Life
The Human Eye
The human eye is an essential sense organ that allows us to see the beautiful world. The specialty of this optical instrument lies hereunder:
Eyes provide us the ability to sense the light and differentiate about 10 million colors.
It can focus on 50 different objects every second.
The eye is the best camera created by God. Yet, some people face difficulty in viewing the nearby or far off objects clearly, while some people don’t get the opportunity to see the world with their open eyes.
Keeping in mind the needs of every individual, around 1285, one of the eyeglass inventors named Salvino D'Armate invented the first vision aid called the reading stone. Slowly and gradually, by modifying technology, visually impaired people also got the chance to look and feel the world around them.
In this article, you will learn about the types of optical instruments that have tossed the scenario of the world by changing the way people see the world around them. So, let us study the optical vision aids.
Optical Low Vision Aids
Myopia: Nearsightedness
Many people face difficulty viewing nearby objects; however, they can see the far off objects with ease. This type of optical defect is known as Myopia.
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In the above figure, we can see that the shape of the eye bends the light, and the image focuses in front of the retina rather than focusing on it.
This optical defect can be rectified by using a Concave Lens. The figure below demonstrates the correction of Myopia:
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Hypermetropia: Longsightedness
An optical defect in which a person can see the far off objects but find difficulties in viewing the nearby objects, such a defect is called the Hypermetropia. This is how it happens:
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Hypermetropia is a common problem where a large image is formed because of the large focal length, causing the nearby objects to appear to blur.
This defect can be corrected by using a converging lens or a convex lens. The figure below demonstrates the way to correct this problem:
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From the above diagram, we can see that a convex lens is kept in front of the eye lens, which forms a virtual image of the near point of the eye, i.e., at a distance of 25 cm, the image gets focused on the retina.
Astigmatism
Astigmatism is a type of refractive error, or we can say it is an imperfection that comes in the curvature of the cornea or lens of the eye such that eyes cannot focus the light uniformly on the retina.
The parallel rays of light coming from infinity form multiple focal points with the accommodation at rest because of which the objects seem blurry at all distances. The figure below demonstrates the astigmatism defect:
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Astigmatic cornea distorts the focus of light in front or beyond the retina. The figure below shows why objects seem blurry at all times:
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For correcting this defect, a particular lens is used called the cylindrical lenses (contact lenses). The figure below demonstrates the correction:
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Presbyopia
An aging eye defect because of which person loses the ability to view the objects clearly with the passing time. It is a physiological inability to accommodate the near vision. A person has to hold a reading material far away to avoid headaches and eye strain. The below figure demonstrates this defect:
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Since this defect is a progressive worsening issue with the age so, people dealing with this issue can use bifocal or progressive eye lenses as a temporary aid for viewing the nearby and far objects, where bifocal lenses have the two following sections:
Primary Section: It is a large section that helps to correct the distance vision.
Secondary Section: It helps us to see nearby objects.
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Visual Aids for Visually Impaired
Who are blind people? Can they see the world around them? The answer to this question is sad No! But they have a superior power to feel; this ability is used as an aid to help them read things as normal people do. This aid is the Braille System.
In the year 1824, the Braille system was invented by Louis Braille. One of the essential aids for Visually Impaired people is the Braille system. Braille or breɪl is the strategic writing system for blind people.
In this system, there are six dots, raised in different patterns to form 26 letters of English; this arrangement of dots, to give English alphabets, is the Braille alphabet. The image below shows the Braille script from A to Z:
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The braille system comprises equivalents for punctuation marks and also imparts symbols to show letter groupings. Braille alphabets are read by moving the hand or hands from left to right along each line.
FAQs on Optical Low Vision Aids for Blind and Visually Impaired Students
1. What are optical aids for visually impaired individuals?
Optical aids are devices that use lenses to help people with low vision see things more clearly. They work by magnifying an image or focusing light correctly on the retina, making it easier to read, write, or see objects that are far away.
2. What are some common examples of optical aids?
Some common optical aids used to assist with low vision include:
- Magnifiers: Simple lenses that enlarge text or small objects.
- Bifocal lenses: Spectacles with two different powers for near and distant vision.
- Contact lenses: Lenses placed directly on the eye to correct vision.
- Telescopic aids: These act like small binoculars to help see distant things, such as a blackboard in a classroom.
3. What is the difference between optical and non-optical aids?
Optical aids use lenses to enhance a person's remaining sight. In contrast, non-optical aids help visually impaired individuals by using other senses, like touch or hearing. For example, a magnifying glass is an optical aid, while a Braille book or a talking clock is a non-optical aid.
4. How does the Braille system work as a non-optical aid?
The Braille system is a tactile reading method. It uses patterns of raised dots to represent letters, numbers, and punctuation. Each character is formed within a small rectangular block called a Braille cell, which has up to six dots. A visually impaired person reads by moving their fingertips along the lines of dots to feel the characters.
5. Why are both types of aids important for a person with low vision?
Both types of aids are important because they address different needs. Optical aids help a person make the most of their remaining vision for specific tasks like reading. Non-optical aids provide alternative ways to access information and navigate the world, which is essential when vision is very limited or for situations where sight is not the primary sense needed.
6. Can modern technology like a smartphone be considered a visual aid?
Yes, absolutely. Modern smartphones and tablets are powerful aids for the visually impaired. They have built-in accessibility features like screen magnifiers, high-contrast modes, and text-to-speech functions that read out on-screen content. Specialised apps can also help identify objects, colours, and currency, acting as both optical and non-optical assistants.
7. How is an optical aid like a hand-held magnifier different from regular eyeglasses?
Regular eyeglasses are designed to correct refractive errors, such as nearsightedness or farsightedness, by focusing light properly onto the retina. An optical aid like a magnifier, however, is used to simply enlarge the image of an object. It is often used by people whose vision cannot be fully corrected with just eyeglasses, helping them see fine details more easily.
